Process for splitting soapstock and apparatus therefor

ABSTRACT

THE INVENTION PROVIDES A PROCESS AND APPARATUS FOR SPLITTING SOAPSTOCK BY ACID TREATMENT TO LIBERATE FREE FATTY ACIDS IN THE FORM OF ACID OIL. THE REACTANT ARE ASPIRATED ONE INTO THE OTHER, PREFERABLY BY THE USE OF THE VENTURI PRINCIPLE, PARTICULARLY IN AN ARRANGEMENT IN WHICH TWO VENTURI PIPES, EACH WITH ITS OWN INDUCTION MANIFILD, ARE ARRANGED IN TANDEM TO DELIVER INTO A COLLECTOLLECTION VESSEL. FIRST ONE REACTANT LIQUID AND THEN THE OTHER IS ASPIRATED THROUGH THE SEPARATE MANIFOLDS BY THE ACTION OF AN ASPIRATING FLUID SUCH AS STEM SERVING THE SYSTEM AND ARE THEREBY INTIMATELY ADMIXED WITH ONE ANOTHER. THE ARRANGEMENT MINIMIZES THE HEAVY CORROSIVE EFFECTS WHICH RESULT FROM THE USE OF MECHANICAL MIXING DEVICES.

Jan. 22, 1974 GADEFMX ETAL 3,787,460

PROCESS FOR SPLITTING SOAPSTOOK AND APPARATUS THEREFOR Filed Dec. 17, 1969 INVENTORS: ROGER GADEFAIX and JEAN KLERE By Their Attorney 2 United States Patent 3,787,460 PROCESS FOR SPLITTING SOAPSTOCK AND APPARATUS THEREFOR Roger Gadefaix, Issy-les-Moulineaux, and Jean Klere,

Colombes, France, assignors to Lever Brothers Company, New York, N.

Filed Dec. 17, 1969, Ser. No. 885,762 Int. Cl. Cllc N00 US. Cl. 260-418 8 Claims ABSTRACT OF THE DISCLOSURE The invention provides a process and apparatus for splitting soapstock by acid treatment to liberate free fatty acids in the form of acid oil. The reactants are aspirated one into the other, preferably by the use of the Venturi principle, particularly in an arrangement in which two Venturi pipes, each with its own induction manifold, are arranged in tandem to deliver into a collection vessel. First one reactant liquid and then the other is aspirated through the separate manifolds by the action of an aspirating fluid such as steam serving the system and are thereby intimately admixed with one another. The arrangement minimizes the heavy corrosive effects which result from the use of mechanical mixing devices.

This invention relates to a process for splitting soapstock and to apparatus suitable for use in the process.

Soapstock is a term commonly applied to the dilute aqueous mixture of soap, oil, and various other components in minor quantity which is obtained as a by-product in the alkali refining of crude vegetable and animal glyceride oils and fats. During this process the free fatty acids present in the crude oils are neutralized by the alkaline medium, forming a soap which, together with some other impurities present in the crude oil, is separated in an aqueous layer from the refined oil. Soapstock consisting essentially of aqueous soap solution may also be obtained as a by-product of other processes.

Soapstock can be used as a starting material for other processes, e.g. the preparation of toilet soap. It is for example known to split the soapstock by stirring it with inorganic acid, in particular concentrated sulphuric acid, in order to liberate free fatty acids in an acid oil from the aqueous phase comprising acid water. These acid oils are recovered by separation and after removal of residual glycerides may be further purified, e.g. by distillation, to make them suitable for use in the preparation of toilet soap.

The total fatty material content of soapstock is often about 10% or even less and in view of the large quantities of liquids involved it is desirable to split it in a continuous manner. However, the development hitherto of an entirely satisfactory continuous process has met with considerable difliculties. The use of mineral acids, in particular concentrated sulphuric acid, creates very difficult corrosion problems, as a result of which it is hardly practi cal to use, for instance, pumps or other devices with rotating and moving mechanical parts to effect the intimate mixing of the acid and the soapstock which is necessary or the transfer of the acid or soapstock/ acid mixture.

Furthermore, relatively long resting times have hitherto been necessary in order to allow the acid oil to separate from the acid water, particularly since as a result of mechanical agitation of the reactant mixture very tenacious emulsions will be often formed which are difficult to break, so that relatively large quantities of acid oil may be entrained with the acid water. In a continuous process this long resting is, of course, not readily effected without losing much of the advantages of continuous processes.

According to the present invention, a process for splitting soapstock for the recovery of acid oil containing free fatty acid comprises reacting the soapstock with an inorganic acid by aspirating one into the other to liberate the free fatty acids by intimately admixing the two reactants and removing from the reaction mixture an acid oil containing the free fatty acids.

The process is preferably carried out by effecting the admixing by using the Venturi principle, one of the reactants being aspirated into the other through the inlet manifold of a Venturi system by the action of a stream of aspirating fluid, comprising the other reactant liquid, flowing through the bore of the Venturi.

The principle of the Venturi is generally used in flow measuring and Water pumps. It consists essentially of a pipe the bore of which tapers over an inlet portion to a minimum at the throat of the Venturi. From the throat the pipe flares in bore over an outlet portion known as the diffuser. In passing through the pipe the flow speed of a fluid stream at first increases to a maximum and its pressure decreases to a minimum at the throat. Thereafter its flow speed decreases and its pressure increases during its passage through the diffuser.

The decrease in pressure produced in the region of the throat may be transmitted through a branch of the pipe to provide an induction manifold enabling liquids to be aspirated into the driving fluid stream in the bore of the Venturi pipe and admix with it in the region of the throat where the turbulent conditions prevailing are favorable for intimate mixing. This is continued as the mixture passes through the difiuser.

In a preferred embodiment of the invention both reactants are aspirated, by using the Venturi principle into a common aspirating fluid, preferably steam, through separate induction manifolds. The invention also provides apparatus for mixing liquids, preferably for carrying out the splitting process described, comprising in combination a Venturi system including inlet and induction manifold means adapted to aspirateone liquid into another by the reduced pressure generated by the passage through the Venturi of an aspirating fluid admitted through the inlet means, and means for collecting the resulting liquid mixture. More particularly the invention rovides an arrangement in which two Venturi systems in tandem, each with its own induction manifold, are served by a common aspirating vapor or gaseous fluid flowing through the bore of each Venturi system in turn. As it passes successively through the Venturi bores the aspirating fluid creates a sub-atmospheric pressure in each induction manifold in turn, thus enabling first one reactant liquid-preferably the acidand then the other to be drawn into the aspirating fluid and hence to intimately admix the two in the throat and diffuser of the second Venturi prior to discharge of the liquid mixture into a collection vessel.

The aspirating action applied in the process of the present invention thus enables the inorganic acid to be delivered to and admixed with the soapstock without the use of devices such as pumps and stirrers with moving parts exposed to the corrosive action of the acid, as in a continuous process.

Where a heated fluid such as steam is used as the aspirating fluid in a Venturi system its heat is transmitted to the reactant liquids aspirated by it, with the effect that reaction is effected much more rapidly than at ambient temperature.

Although any inorganic acid in liquid form can be used in the process of the invention which is capable of liberating the free fatty acids, a liquid mineral acid, for example hydrochloric acid, but particularly sulphuric acid is preferred, particularly at a concentration of 20-30 N. This acid, being in a relatively concentrated form contributes to heating the mixture as a result of the liberation of heat of dilution when it is used, again ensuring rapid reaction.

After the mixing has been effected by aspiration, the reaction mixture is preferably passed through a pressure equalizing chamber connected with the outside atmosphere to avoid any disturbing pressure fluctuations before being further processed. Excess gaseous or vaporous fluid, including aspirating fluid where this is used may be separated at this point from the liquid stream through a vent to atmosphere. The liquid reaction product mixture is collected preferably after passage through a packed zone to ensure even more complete mixing. The velocity of the mixture admitted into the separating vessel is preferably reduced considerably to enable virtually complete separation of the liquid reaction product to be effected in the separating vessel into an upper oily phase comprising acid oil containing the liberated fatty acids and residual glycerides and a lower aqueous phase comprising acid Water. This reduction in velocity is preferably effected by admitting the mixture into a separating vessel having a cross-sectional area of -100 times that of the inlet to it. The provision of a packed zone is also preferred downstream of the vent to atmosphere, prior to the introduction of the mixture into the separating vessel.

Although the process is particularly useful in the treatment of soapstocks obtained from the refining of crude glyceride oils, it will be understood that soap solutions originating from other processes may also be used in the process of the present invention, for example soap solutions obtained in the preparation of synthetic fatty acids. The presence of glycerides in the soapstocks or in the acid oil is not therefore essential to the operation of the process of the invention.

A suitable form of apparatus for carrying out the process of the present invention is illustrated in the accompanying drawings in which FIG. 1 is a schematic representation of the upper part of the apparatus where the reactant liquids are mixed and FIG. 2 is a similar representation showing the total apparatus, including the separating vessel, drawn on a smaller scale and omitting the internal details already shown in FIG. 1.

Referring to FIG. 1, the upper part of the apparatus comprises interconnected coaxial pipes 1, 3 and 4. Each is of general uniform bore.

The two Venturi pipes are arranged in tandem and provided by upper and lower internal tubes inside the pipe 3, which is also furnished with upper and lower side arms 7 and 8 providing induction manifolds for the two Venturi systems.

Pipe 1 of narrowest bore enters pipe 3, terminating in a jet orifice 2 to provide an inlet for the first Venturi. The upper part of the first internal tube provides a mouth for the first Venturi pipe, surrounding the lower end of pipe 1 and extending with tapering bone to the throat 5 in the region of the orifice 2, h'om a position where it is sealed to the internal wall of pipe 3 between the sidearms 7 and 8. The lower end of the first internal tube constitutes the diffuser 6 of the first Venturi, the bore of the tube expanding in this region, from the throat 5, which is however somewhat wider in bore than pipe 1, to provide an outlet orifice from the first Venturi at the lower end of the tube.

. The inlet for the second Venturi system is provided by e Out et orifice of the diffuser 6. The upper end of the lower of the internal tubes within pipe 3, constituting the pipe of the second Venturi, furnishes a mouth 9 surrounding the outlet end of the diffuser 6 and again tapers to its narrowest bore at the throat. The diffuser 14 provided by the lower end of the second internal tube similarly expands from the throat down its length, but to a position where it is sealed to the internal wall of the pipe 3, below the second sidearm 8.

Pipe 4 constitutes a pressure equalizing vessel. This is connected to the diffuser 14 of the second Venturi system by the bottom end of pipe 3 and is furnished by a vent 11 connecting the vessel to atmospheric pressure to smooth out any pressure fluctuations in the vessel and disengage gases and vapors from the liquid products. The pressure equalizing vessel 4 is also equipped with entry port 12 for the introduction of measuring or controlling devices into the vessel.

A packed bed 10 occupies a substantial proportion of the interior space of the vessel 4. Liquid entering the vessel passes through the packed bed 10 and leaves through the outlet pipe 13. Referring now to FIG. 2, the outlet pipe 13 from the pressure equalizing vessel extends to its outlet 19 into the interior of a separating vessel 15. This is equipped with ports 21 and 22 located in the upper and lower parts of the vessel.

The outlet 19 is buried in a packed bed 16 which fills the middle portion of the separating vessel 15 from the sieve base 17 on which the bed is supported in the vessel to its level 18 above the outlet 19 of the pipe 13. In order to limit throughput as little as possible, the packing selected for the packed bed 16 preferably affords a free space of about 70-95% of the total volume which is occupied. To meet this requirement the packing bodies are preferably composed of large cylinders or saddles of an inert material e.g. glass, porcelain, glazed porcelain or stainless steel. The packed bed 10 of the separating vessel 4 in the FIG. 1 is preferably composed of similar material.

The apparatus is composed of a material of adequate structural strength which is inert to the reactants e:g. glass or is lined with an inner inert material e.g. acid-resistant enamel.

In using the apparatus illustrated in FIGS. 1 and 2 in accordance with the invention, the induction manifolds 7 and 8 are connected to mineral acid and soapstock supplies and pipe 1 to a steam supply to serve the Venturi system. The steam issuing from the jet orifice 2 enters the mouth of the first Venturi pipe increasing its velocity and reducing its pressure as it passes through the throat 5. This reduction in pressure is transmitted to the induction manifold 7, thus aspirating asupply of acid into the Venturi pipe which becomes entrained in and heated by the steam.

Upon emerging into the diffuser 6 from the obstruction provided by the throat 5 the :aspirating fluid, now comprising a mixture of steam and heated acid, decreases somewhat in velocity before entry through the outlet end of the diffuser 6 of the first Venturi into the mouth 9 of the second Venturi pipe. Once more the speed of flow of the fluid increases to a maximum in passing through the throat of the second Venturi pipe. This again creates a reduction in pressure in the region of the throat which is communicated to the soapstock supply via the induction manifold 8.

The soapstock is aspirated through the induction manifold 8 to mix with the aspirating fluid already containing the mineral acid. Both the heat of dilution as well as the heat of reaction can contribute to heating the mixture. Mixing is substantially complete by the time the mixture emerges from the diffuser 14 into the bottom part of the tube 3. The liquid components of the mixture pass through the bed 10 in the pipe 4, in which the flow speed of the fluid mixture emerging from the pipe 3 is substantially decreased. The pressure in the pipe 4 is maintained at atmospheric pressure by the vent 11, thereby minimizing surge effects in the How of fluid, and ensuring the discharge of excess steam to atmosphere.

The liquid products emerge from the pressure equalizing vessel provided by pipe 4, flowing down pipe 13 into the packed bed supported in the separating vessel 15. The product mixture rapidly separates into a lower aqueous layer, comprising acid water removed from the vessel 15 through the lower port 22, and an upper organic layer comprising the acid oil product, through the upper port 21.

A suitable form of the apparatus illustrated, which is capable of treating soapstock at a rate of 6-13 tons per meter sq. per hour, has the following dimensions:

Preferably the temperature of steam used as the driving fluid is l120 C. The soapstock and/or the mineral acid may be used at room temperature, particularly if the latter is sulphuric acid. In apparatus with these dimensions, soapstock can be treated with a throughput from 6-13 tons/mF/hour.

EXAMPLE A coconut oil soapstock containing 10% fatty matter and obtained by neutralizing crude coconut oil containing free fatty acids with aqueous alkali was treated to recover the fatty acids in the apparatus described with reference to FIGS. 1 and 2, having the above dimensions. Steam was introduced into the apparatus through pipe 1 at a pressure of 0.5 kg./cm. and a temperature of 110 C.; aspirating into the Venturi system first 27 N sulphuric acid, at room temperature and then the soapstock at 85 C. through the induction manifolds 7 and 8. The pressure equalizing vessel 4 and the separation vessel -15 were each furnished with packed beds consisting of glass Raschig rings having a characteristic value of 50 mm., through which the reacted mixture passed.

The separation vessel 15 was kept filled and the acid oil continuously withdrawn through the upper outlet 21 had a water content of 1% and a soap content below 0.1% and contained only traces of sulphuric acid. The acid water, similarly drawn through the lower outlet 22, had a pH of 0.1.

When the process was repeated, using palm oil soapstock obtained in a similar manner and containing 5% fatty matter, the acid oil water content was about 1.3%, its soap content less than 0.1% and mineral acid content even less. The pH of the acid water was again 0.1.

What is claimed is:

1. Process for splitting soapstock containing combined fatty acids by reaction of the soapstock with inorganic acid in liquid form which is capable of liberating the fatty acids, characterized by the following sequence of steps:

(a) continuously aspirating one reactant into a stream of the other by using the Venturi principle to effect their intimate admixture,

(b) collecting the liquid products of tne mixture thus obtained, and

(c) separating an acid oil layer containing the free fatty acid from the collected liquid products.

2. Process according to claim 1 wherein the liquids are aspirated in turn into a stream of aspirating fluid by using the Venturi principle.

3. Process for splitting soapstock containing combined fatty acids by reaction of a soapstock with inorganic acid in liquid form which is capable of liberating the fatty acids, characterized by the following sequence of steps:

(a) aspirating the liquid reactants in turn into a stream of an aspirating fluid selected from vapors and gases 'by using the Venturi principle,

(b) disengaging the aspirating medium from the liquid product of the mixture thus obtained,

(c) collecting the liquid products thus obtained, and

(d) separating from the liquid products an oily layer containing the free fatty acids.

4. Process according to claim 3 wherein the aspirating fluid comprises steam.

5. Process according to laim 3 wherein the reaction, mixture is passed through at least one bed of inert pack- References Cited UNITED STATES PATENTS 2,758,122 8/1956 Clayton 260397.25

3,027,388 3/1962 Smith, Jr. et al 260410.9

2,328,892 9/1943 Colgate et a1 260-418 2,232,544 2/1941 Lorenz 260'-418 FOREIGN PATENTS 714,608 8/1954 Great Britain 260-424 LEWIS GO'ITS, Primary Examiner E. G. LOVE, Assistant Examiner US. Cl. X.R. 55-257; 260-424 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,787,460

DATED 3 January 22, 1974 INVENT0R(5) 1 Roger Gadefaix et al.

it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading:

Column 1, line 8: add the words Claims priority, application France, December 17, 1968 178690 Signed and Scaled this Seventeenth Day Of October I978 [SEAL] Attest:

DONALD W. BANNER RUTH (I MASON Attesting Ojficer Commissioner of Patents and Trademarks 

